1. Field of the Invention
The present invention relates to a lip type seal corresponding to one kind of a sealing apparatus. The lip type seal in accordance with the present invention is used, for example, as a shaft seal or the like for a water pump (W/P) for a vehicle such as a motor vehicle or the like, or is used as a shaft seal for a W/P for a consumer electrical appliance or a light load industrial use.
2. Description of the Conventional Art
Conventionally, as shown in FIG. 9, there has been known a lip type seal 81 which is installed to an inner periphery of a shaft hole 72a of a housing 72 and slidably comes into close contact with a peripheral surface of a shaft 74 inserted to the shaft hole 72a, thereby inhibiting a sealed fluid within the machine from leaking out to an atmospheric air side, and this lip type seal 81 has a first seal lip 82 which is arranged in a sealed fluid side A and is made of a rubber-like elastic material, and a second seal lip 83 which is arranged in an atmospheric air side B and made of a resin (refer to patent document 1).
Since the conventional lip type seal 81 mentioned above has a plurality of seal lips 82 and 83 each of which performs a seal operation, an excellent seal effect can be achieved, however, has a disadvantage in the following point.
In particular, on the basis of necessity for recycle in an environmental problem in recent years, it is required to dispose of each of constructing parts of the lip type seal after being sorted on material, however, in the conventional lip type seal 81 mentioned above, the first lip seal 82 made of the rubber-like elastic material is bonded via vulcanization to a reinforcing ring 84 made of a metal, and both the elements 82 and 84 are formed as an integral vulcanization molded product. Accordingly, it is impossible to easily separate and sort both the elements 82 and 84 at a time of disposing, and it is therefore impossible to comply with the necessity for the recycle mentioned above.
Accordingly, the applicant of the present invention has proposed a lip type seal 91 having a first lip seal member 92 provided with a first seal lip 93 arranged at a sealed fluid side A and made of a rubber-like elastic material, a second lip seal member 94 provided with a second seal lip 95 arranged at an atmospheric air side B and made of a resin, and two cases 96 and 97 pinching both the lip seal members 92 and 94 from both sides in an axial direction and made of a metal, and having a structure in which these four parts are assembled without being bonded, as shown in FIG. 10 (refer to patent document 2). In accordance with this prior art, since each of the parts is not bonded, it is possible to easily separate and sort each of the parts. Accordingly, it is possible to comply with the necessity for the recycle mentioned above. However, in the prior art, there is room of improvement in the following points.
(1) Assembly Retaining Characteristic Between Constructing Parts
In particular, in the lip type seal 91 mentioned above, two cases 96 and 97 are respectively structured such as to have annular flat surface portions 96a and 97a for pinching both the lip seal members 92 and 94 from both sides in an axial direction and have tubular portions 96b and 97b integrally formed with the flat surface portions 96a and 97a, and the tubular portions 96b and 97b are fitted to an inner peripheral side of a cylinder portion 92a of the first lip seal member 92 in the case 96 at the sealed fluid side A, and are pressure inserted and fixed to an insertion hole 92b provided in the cylinder portion 92a of the first lip seal member 92 in the case 97 at the atmospheric air side B. Accordingly, each of the parts is retained in an assembled state on the basis of setting of a fitting margin and a pressure inserting margin required for the fitting and the pressure insertion, however, an engagement structure for preventing a separation in an axial direction among the parts in the case that each of the parts is exposed to force in the axial direction is not particularly provided among the parts. Therefore, if the case 96 at the sealed fluid side A is pulled in an axial direction (a direction of an arrow C) so as to detach the lip type seal 91 in a state of being installed to an inner periphery of the shaft hole 72a of the housing 72, there is a case that only this case 96 is pulled out and the other parts remain in an installed state (alternatively, there may be a case that only the case 96 and the first lip seal member 92 are pulled out, and the second lip seal member 94 and the case 97 at the atmospheric air side B remain). This is nothing but the assembling and retaining force among the parts is dependent only upon friction force.
(2) Installing Workability
Further, in the lip type seal 91 mentioned above, two cases 96 and 97 do not particularly have any structure for defining an interval in an axial direction therebetween. Further, the first lip seal member 92 pinched between both the elements and made of the rubber-like elastic material can achieve a sufficient seal operation only by being used in a state of being compressed in the axial direction. In other words, there is a risk that a leak of a sealed fluid is caused from the portion between the first lip seal member 92 and the second lip seal member 94 made of the resin or the case 97 at the atmospheric air side B. Accordingly, at a time of installing the lip type seal 91 mentioned above, the lip type seal 91 is installed by using a snap ring 99 while bringing the lip type seal 91 into contact with a step portion 98 provided in an inner periphery of the shaft hole 72a of the housing 72 so as to apply a compression load in the axial direction, whereby the lip type seal 91 is installed in a state in which a whole thereof is compressed in the axial direction between the step portion 98 and the snap ring 99. However, there is such a disadvantage that a work of installing by using the snap ring 99 while applying the compression load in the axial direction as mentioned above is extremely complicated.
Further, since the cylinder portion 92a of the first lip seal member 92 is provided with the annular insertion hole 92b which is open to the atmospheric air side B, a portion at an outer peripheral side from the insertion hole 92b in the cylinder portion 92a is formed in such a shape that the atmospheric air side end portion 92c is terminated in the cylindrical shape. Accordingly, since the atmospheric air side end portion 92c rubs the inner peripheral surface of the shaft hole 72a at a time of inserting the first lip seal member 92 into the inner periphery of the shaft hole 72a of the housing 72, there is a case that an evagination is generated at the atmospheric air side end portion 92c. 